JP6422803B2 - Column base joint structure - Google Patents

Description

  The present invention relates to a column base joint structure of a reinforced concrete building having a plurality of layers.

  In a reinforced concrete structure in which a skeleton is composed of columns and beams, the column beam joint is generally rigidly joined. In such a building, since the bending stress is concentrated at the joint between the column base and the footing, pile, foundation beam, or other foundation structure, it is necessary to increase the cross section of the column lower part and the foundation structure.

  In recent years, it has been proposed that the lowermost column base be joined to the foundation structure by a semi-rigid joint. For example, Patent Document 1 discloses a column base and a stigma having a small cross section and a small number of main bars as compared with an intermediate part of a column. Such a joint structure between the column base and the slab and the lower and upper slabs is for forming a uniform deformation mode in the height direction, and is bent and yielded earlier than other joint structures during an earthquake. The moment is reached and a hinge is formed.

JP 2014-136888 A

  However, in the joint structure described in Patent Document 1, not only the bending strength but also the strength against axial force and shearing force is reduced.

  In view of such a background, the present invention provides a column base for a reinforced concrete building having a plurality of layers in which bending strength is reduced in order to avoid stress concentration in the lowermost layer and reduction in other strength is suppressed. An object is to provide a joint structure.

  One aspect of the present invention is a column-base joint structure (2, 28, 48) for a building having a plurality of layers formed to avoid stress concentration in the lowermost layer, which is a reinforced concrete foundation structure (4 , 30, 50), the first pillar bars (18, 40) which are erected on the foundation structure and are connected to the foundation structure and extend in the vertical direction, and are not connected to the foundation structure. A reinforced concrete column having second column bars (20, 42) extending in the vertical direction, and a thin film or plate-shaped edge cutting member (22, 22) disposed at least at a part between the foundation structure and the columns. 46).

  According to this configuration, since the concrete is not adhered between the foundation structure and the column by the edge cutting member, it is possible to prevent the propagation of cracks without affecting the shaft strength.

  According to another aspect of the present invention, in the above configuration, the column includes an intermediate portion (12, 38) extending in the vertical direction, and a lower end portion (14, 34) having a reduced cross section than the intermediate portion. The edge cutting member is arranged on the lower surface (14a, 34a) of the lower end portion.

  When the bending force is applied, the fulcrum is the outer periphery of the bottom surface of the column. However, according to this configuration, the fulcrum is close to the center axis of the column, so the amount of deformation of the concrete part around the fulcrum is reduced, and the concrete Damage to the part can be suppressed.

  Another aspect of the present invention is characterized in that, in the above configuration, the substructure (30, 50) has a recess (36) for receiving the lower end of the column (32).

  According to this configuration, the shear force is transmitted by the bearing pressure between the inner side surface of the recess and the outer peripheral surface of the lower end portion of the column, and the shear strength is reduced due to the fact that the column and the foundation structure are not integrated. Can be supplemented.

  Another aspect of the present invention is characterized in that, in the above configuration, the steel pipe (16) filled with the lower end portion of the column is further provided. Another aspect of the present invention is characterized in that, in the above configuration, the lower end portion of the column is formed of concrete having a higher strength than the intermediate portion.

  According to these structures, the axial strength of the lower end part thinner than the intermediate part can be supplemented in the column.

  According to another aspect of the present invention, in the above-described configuration, the side surface of the lower end portion of the column is surrounded, and between the lower surface (12a, 38a) of the intermediate portion and the upper surface (30a, 50a) of the substructure. A joint member (26) to be arranged is further provided.

  According to this configuration, the lower surface of the intermediate portion and the upper surface of the substructure are provided even if the lower end portion having a reduced cross section is provided in order to reduce the bending resistance due to the lower surface of the pillar contacting the upper surface of the substructure. Since the joint member is disposed between the two, the appearance is not impaired.

  Another aspect of the present invention is characterized in that, in the above-described configuration, the first pillar (18) penetrates the edge cutting member (22).

  According to this configuration, the arrangement of the first column bars can be set without being restricted by the arrangement of the edge cutting members.

  Another aspect of the present invention is characterized in that, in the above-described configuration, the first columnar bars (40) are arranged at positions shifted in a horizontal direction with respect to the edge cutting member (46).

  According to this configuration, since the first column bars are connected to the foundation structure at a position avoiding the edge cutting member, it is possible to save the trouble of processing such as opening a hole in the edge cutting member, and the workability is improved.

  According to the present invention, it is possible to provide a column-base joint structure for a building having a plurality of layers in which bending strength is reduced in order to avoid stress concentration in the lowermost layer and reduction in other strength is suppressed. .

The longitudinal cross-sectional view of the column-base joining structure according to the first embodiment Cross-sectional view of the column base joint structure according to the first embodiment Longitudinal sectional view of the column base joint structure according to the second embodiment Longitudinal sectional view of a column base joint structure according to a modification of the second embodiment

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each figure, in order to avoid complication of the figure, some illustrations of reinforcing bars and hatching are omitted.

<< First Embodiment >>
First, a first embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a vertical cross-sectional view (II cross section in FIG. 2) of the column base joint structure 2 according to the first embodiment, and FIG. 2 is a cross-sectional view (II-II cross section in FIG. 1). The column base joint structure 2 is a structure in which a reinforced concrete pillar 6 is joined to a footing 4 which is a reinforced concrete foundation structure, and is applied to the lowest layer of a building having a plurality of layers.

  The footing 4 is a reinforced concrete member that transmits the load from the pillar 6 to the ground, and extends in the horizontal direction. The footing 4 includes a horizontal footing main reinforcement 8, a vertical extension and a lower end side entering a pile (not shown) to fix the footing 4 to the pile, and a stirrup (not shown). ).

  The column 6 is a reinforced concrete member that supports the load of the superstructure of the building and transmits the load to the footing 4, and is erected on the footing 4. The column 6 has an intermediate portion 12 having a prismatic shape extending in the vertical direction, and a lower end portion 14 having a smaller cross section than the intermediate portion 12. The lower end portion 14 has a rectangular shape or a square shape in a plan view, and the front and rear and left and right widths of the intermediate portion 12 are narrow. The lower surface 14a of the lower end part 14 and the rectangular ring-shaped lower surface 12a of the intermediate part 12 are horizontal planes.

  The lower end portion 14 of the column 6 is formed by filling the steel pipe 16 with concrete. Instead of using the steel pipe 16 or together with using the steel pipe 16, the lower end portion 14 may be made of concrete having higher strength than the intermediate portion 12.

  The column 6 is connected to the footing 4 to extend in the vertical direction, the first column 18, the second column 20 extending in the vertical direction without being connected to the footing 4 and forming the main bar of the column 6, and the hoop. (Not shown). The imaginary line in FIG. 2 shows the outline of the lower end portion 14. Each of the first columnar bars 18 extends from the intermediate portion 12 through the lower end portion 14 to the inside of the footing 4 and is arranged so as to be aligned on a rectangular outline that is slightly smaller than the lower end portion 14 in plan view. . Since the lower end side of the first pillar 18 enters the footing 4, the first pillar 18 connects the pillar 6 and the footing 4. The second columnar bars 20 are arranged so that the lower ends thereof are located in the vicinity of the lower ends of the intermediate portions 12 and are arranged on a rectangular outline that is slightly larger than the lower end portions 14 in plan view. Since the second pillar 20 does not enter the footing 4, the pillar 6 and the footing 4 are not connected. The total cross-sectional area of the first column 18 is smaller than the total cross-sectional area in the middle portion 12 of the column 6 of the second column 20 that is the main reinforcement of the column 6.

  A steel plate 22 is disposed between the lower surface 14 a of the lower end portion 14 of the column 6 and the upper surface 4 a of the footing 4 as an edge cutting member for cutting the concrete edge between the column 6 and the footing 4. The plate 22 is a flat plate and has a quadrangular shape that substantially matches the contour of the lower end portion 14 in plan view. The plate 22 is provided with a hole 24 through which the first pillar 18 is inserted. Instead of a plate-like member such as the plate 22, a thin-film member may be used as the edge cutting member.

  A joint member 26 is disposed in the gap between the lower surface 12 a of the intermediate portion 12 of the column 6 and the upper surface 4 a of the footing 4. The joint member 26 is preferably made of a flexible and buffering resin such as polyethylene foam, surrounds the side surface of the lower end portion 14, and the outer peripheral surface is aligned with the side surface of the intermediate portion 12.

  The effects of the column base joint structure 2 will be described. The total cross-sectional area of the first column 18 is smaller than the total cross-sectional area of the second column 20 that is the main reinforcement of the column 6, and the first column 18 is arranged inside the second column 20. Therefore, compared to a structure in which all the main bars are connected to the foundation, the joint portion between the column 6 and the footing 4 has a low yield strength against bending. Therefore, in a building having a plurality of layers, stress concentration on the lowermost layer can be avoided, and the cross section of the footing 4 can be reduced.

  Note that the first column 18 functions as the main reinforcement of the column 6 in the sense of resisting bending. In addition, it can be said that the first column reinforcement 18 constitutes the main reinforcement of the column 6 in that it is arranged with a predetermined covering along the outer periphery of the lower end portion 14 of the column 6. The first column 18 extends from the lower end portion 14 of the column 6 to the footing 4, and may extend in the vertical direction at least by the fixing length in the intermediate portion 12 of the column 6. It does not have to extend over the entire height.

  Moreover, in this embodiment, since the edge of the concrete part of the column 6 and the footing 4 is cut by the plate 22, crack propagation and bending stress are not adversely affected in the axial strength of the lower end part 14 in the concrete part. Transmission is prevented. Further, by providing the holes 24 in the plate 22, it is possible to place the first column 18 close to the central axis of the column 6, and when the bending stress is applied, the first column 18 is arranged. The force acting in the pulling direction can be suppressed.

  Since the cross-sectional area of the lower end portion 14 of the column 6 is smaller than that of the intermediate portion 12, the axial strength is reduced when no reinforcement is performed. In the present embodiment, the axial strength of the lower end portion 14 is reinforced by the confinement effect by the steel pipe 16 and the use of high-strength concrete for the lower end portion 14.

  When the lower surface 14 a of the lower end portion 14 of the column 6 comes into contact with the upper surface 4 a of the footing 4, it resists bending. In order to reduce this resistance, the cross section of the lower end portion 14 is reduced. However, since the joint member 26 is disposed between the lower surface 12a of the intermediate portion 12 and the upper surface 4a of the footing 4, the appearance is not impaired. .

<< Second Embodiment >>
Next, with reference to FIG. 3, the column-base joining structure 28 according to the second embodiment of the present invention will be described. In addition, the same code | symbol is attached | subjected to the structure similar to 1st Embodiment, and the description is abbreviate | omitted. FIG. 3 is a longitudinal sectional view of the column base joint structure 28 according to the second embodiment.

  The reinforced concrete footing 30 is provided with a recess 36 for receiving the lower end 34 of the column 32. The recessed part 36 is a shape which complementarily receives the lower end part 34 of the pillar 32, and the bottom face 36a is a horizontal plane.

  The reinforced concrete column 32 erected on the footing 30 is similar to the column 6 of the first embodiment in terms of the outer shape of the concrete part, and includes an intermediate portion 38 and a lower end portion 34 whose cross section is smaller than that of the intermediate portion 38. Have The lower end 34 is surrounded by the steel pipe 16 as in the first embodiment, and may be formed of concrete having a higher strength than the intermediate portion 38. Further, when the outer peripheral surface of the steel pipe 16 and the inner peripheral surface of the recess 36 are in contact with or close to each other and there is a gap between them, a grout or the like may be filled in the gap.

  The column 32 includes a first column bar 40 connected to the footing 30, a second column bar 42 not connected to the footing 30, and a hoop (not shown). The first column bars 40 and the second column bars 42 both extend in the vertical direction and constitute the main bars of the column 32. Each of the first columnar bars 40 is arranged so as to line up on a rectangular outline that is slightly larger than the lower end part 34 in plan view, and the lower end side thereof enters the footing 4. Each of the second columnar bars 42 is arranged so as to line up on a rectangular outline that is slightly smaller than the lower end part 34 in plan view, and the lower end thereof is located in the lower end part 34 of the column 6. The first column reinforcement 40 adheres to the concrete of the pillar 32 on the upper end side and adheres to the concrete of the footing 30 on the lower end side, but a predetermined length from the lower end side of the intermediate portion 38 of the pillar 32 to the upper side of the footing 30. In the range, it is disposed in the sheath 44, and the sheath 44 is not filled with a filler such as grout and is not attached to concrete.

  A steel plate 46 is disposed between the lower surface 34 a of the lower end 34 of the column 32 and the bottom surface 36 a of the recess 36 of the footing 30. The plate 46 is a flat plate and has a quadrangular shape that substantially matches the contour of the lower end portion 14 in plan view.

  The joint member 26 is disposed in the gap between the lower surface 38 a of the intermediate portion 38 of the column 32 and the upper surface 30 a of the footing 30. The joint member 26 is preferably made of a soft and cushioning resin such as polyethylene foam, and surrounds the upper portion of the side surface of the lower end portion 34, and the outer peripheral surface is substantially aligned with the side surface of the intermediate portion 38.

  The operational effects of the column base joint structure 28 according to the second embodiment will be described. The first column bars 40 that connect the columns 32 and the footings 30 are arranged outside the columns 32 as compared to the first embodiment, but the first column bars 40 are made of concrete in the sheath 44. Since it is not attached, the portion of the first columnar muscle 40 in the sheath 44 is more easily deformed than the other portions. Although it resists the bending force at this portion, since the second column reinforcement 42 does not connect the column 32 and the footing 30, the resistance to bending is lower than the structure in which all the main reinforcements connect both. Thus, in a building having a plurality of layers, stress concentration on the lowermost layer can be avoided, and the cross section of the footing 30 can be reduced.

  Since the lower end portion 34 of the column 32 is fitted in the recess 36 of the footing 30, the shearing force is transmitted by the side surfaces of both sides supporting each other. This compensates for a decrease in shear strength due to the fact that the pillar 32 and the footing 30 are not integrated.

  Since the edge of the concrete portion between the column 6 and the footing 4 is cut by the plate 46, the propagation of cracks is prevented in the concrete portion without adversely affecting the axial strength of the lower end portion 14.

  The confining effect by the steel pipe 16, the reinforcement of the axial strength of the lower end 34 when the high strength concrete is used for the lower end 34, the function of the joint member 26, and the like are the same as in the first embodiment.

<< Modification of Second Embodiment >>
Next, with reference to FIG. 4, a column base joint structure 48 according to a modification of the second embodiment will be described. In addition, the same code | symbol is attached | subjected to the structure similar to 2nd Embodiment, and the description is abbreviate | omitted. FIG. 4 is a longitudinal sectional view of a column base joint structure 48 according to a modification of the second embodiment.

  The column base joint structure 48 bulges so that a part of the upper surface 50a of the footing 50 is higher than the floor level SL, and the column 32 is erected on the bulged portion. In other respects, the second embodiment has the same configuration and operational effects as the second embodiment.

  Although the description of the specific embodiment is finished as described above, the present invention is not limited to the above embodiment and can be widely modified. For example, you may provide the recessed part which receives the lower end part of a pillar like 2nd Embodiment in the footing of 1st Embodiment. The shape of the cross section of the pillar may be another polygon, a circle, an oval, or the like instead of the quadrangle. Moreover, in 2nd Embodiment, you may arrange | position the lower end in a pillar as a 2nd column reinforcement which does not make the 1st column reinforcement which connects all the main bars of the outer peripheral side with a footing, but a part thereof. . The column may be cast-in-place concrete or precast concrete.

2, 28, 48 ... column base joint structure, 4, 30, 50 ... footing (base structure), 6, 32 ... pillar, 12, 38 ... intermediate part, 14, 34 ... Lower end, 16 ... Steel pipe, 18, 40 ... First column, 20, 42 ... Second column, 22, 46 ... Plate, 26 ... Joint member

Claims (6)

A column base joint structure of a building having a plurality of layers formed to avoid stress concentration on the lowest layer,
Reinforced concrete foundation structure,
A first columnar bar which is erected on the substructure and extends in the vertical direction connected to the substructure; and a second columnar bar which extends in the vertical direction without being connected to the substructure. Reinforced concrete pillars with
A thin film or plate-shaped edge cutting member disposed at least in part between the foundation structure and the pillars ;
The columnar joint structure according to claim 1, wherein the first column bar penetrates the edge cutting member or is disposed at a position shifted in a horizontal direction with respect to the edge cutting member . The column has an intermediate part extending in the vertical direction, and a lower end part whose cross section is reduced more than the intermediate part,
The column base joint structure according to claim 1, wherein the edge cutting member is disposed on a lower surface of the lower end portion.   The column base joint structure according to claim 2, wherein the foundation structure has a recess that receives the lower end portion of the column.   The column base joint structure according to claim 2, further comprising a steel pipe filled with the lower end portion of the column.   The column base joint structure according to any one of claims 2 to 4, wherein the lower end portion of the column is formed of concrete having higher strength than the intermediate portion.   The joint member according to any one of claims 2 to 5, further comprising a joint member that surrounds a side surface of the lower end portion of the column and is disposed between a lower surface of the intermediate portion and an upper surface of the foundation structure. Column base joint structure as described.

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